app.py

import os
from flask import Flask, abort

app = Flask(__name__)

healthy = True

@app.route("/env/var")
def env_var():
    return "VAR: {}\n".format(os.environ["VAR"])

@app.route("/")
def root():
    return "/toggle to toggle healthyness\n/healthz to get response\n"

@app.route("/toggle")
def hello():
    global healthy
    healthy = not healthy
    return "now {}\n".format(healthy)

@app.route("/healthz")
def healthz():
    if healthy:
        return "healthy\n"
    else:
        abort(400)


if __name__ == "__main__":
    app.run(debug=True, port=80, host="0.0.0.0")

Dockerfile

FROM python:3

COPY requirements.txt /
RUN pip install --no-cache-dir -r /requirements.txt
RUN apt-get update && apt install -y curl

COPY . /data

CMD ["python", "/data/app.py"]

requirements.txt

flask